Fringing-RF-Field-Activated DC-to-Pulse Converter at the SCRIT Electron Scattering Facility

Abstract

We developed a new-type of dc-to-pule converter, called FRAC (Fringing-Rf-field-Activated dc-topule Converter), for low-energy ion beams. This is based on a RFQ linear trap technique and works under ultra-high vacuum conditions. Ions continuously injected into FRAC are decelerated by an alternating longitudinal electric field produced in a distorted RF field around the edge region of RFQ rods. These ions accumulate in FRAC for a significantly long time. They are stacked during the FRAC operation period and consequently ejected as a high intensity pulsed beam. This edge effect appears most notably when the energy of incoming ions is below several eV at the injection barrier and the energy spread is considerably small. The peak intensity of the output pulsed beam achieved in practice was 112-times larger than the dc-beam intensity at the FRAC operation frequency of 1 Hz.